Nobody who has it talks about it and no one else is sure about its actual numbers. But space-based electronic intelligence, the realm that India just forayed into with the launch of Monday’s defence satellite EMISAT, is said to have been around since the early 1960s, pioneered by the U.S.

At least three other space powers are said to be past masters at it – the U.S. as the leader is said to be having fifth-generation ELINT satellites; Russia is not far behind. And of late, China as the new space force to reckon with is believed to have two special constellations, according to the web and a few informed sources. An estimated 150 military satellites may be hovering all over Earth right now.

These satellites can locate where radars are; figure out what signals they send out in order to enable right actions; eavesdrop on radar communication; and much more.

Senior people in the Defence Research & Development Organisation (DRDO) — which created the EMISAT’s brain or payload — are not too happy that their new baby is being publicly discussed. An otherwise transparent ISRO which launched EMISAT on its PSLV rocket has been coy about its details and uses but perhaps could not avoid naming it under its civil-sector mandate.

“It is disappointing that the whole world now knows what we have. It just defeats the purpose for which it was put up,” regretted a DRDO official privy to key programmes.

According to a few present and former defence scientists, one satellite for ELINT will not suffice and the country may need to have at least three more working in tandem. And this could be the beginning of a new set of space-based military surveillance, the official said.

In the space era, “The forces need many things based in space, such as for electronic intelligence, signal intelligence, communication intelligence, and image intelligence.”

“Today, everything is in space, which adds the fourth dimension to the forces,” said the DRDO official, who does not wish to be named. Ground-based or aircraft-based radars have a few locational limitations. A well-equipped satellite perched high up is an asset that can generate vast information vital for the country's defence against attacks from outside, according to the official.

Coincidentally EMISAT has been flown days after DRDO achieved another publicly broadcast feat on March 27 — that of the launch of the anti-satellite missile, the ASAT.